Method for forming a porous reaction injection molded chemical mechanical polishing pad

ABSTRACT

The present invention provides a method of forming a chemical mechanical polishing pad comprising, providing a tank with polymeric materials, providing a storage silo with microspheres and providing an isocyanate storage tank with isocyanates. The invention further provides delivering the polymeric materials and the microspheres to a premix prep tank, forming a pre-mixture of the polymeric materials and the microspheres, delivering the pre-mixture to a premix run tank and forming a mixture of the pre-mixture and the isocyanates. Further the invention provides injecting the mixture into a closed mold, curing the polishing pad in the mold and degassing at least one of the tank, isocyanate storage tank and the mold.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 60/669,321 filed Apr. 6, 2005.

BACKGROUND OF THE INVENTION

The present invention relates to polishing pads for chemical mechanicalplanarization, and in particular, relates to polishing pads formed by areaction-injection molding process (RIM). Further, the present inventionrelates to apparatuses and methods for forming porous polishing padsformed by a RIM process.

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited on or removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting, and dielectric materials maybe deposited by a number of deposition techniques. Common depositiontechniques in modern processing include physical vapor deposition (PVD),also known as sputtering, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), and electrochemicalplating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the wafer becomes non-planar. Because subsequentsemiconductor processing (e.g., metallization) requires the wafer tohave a flat surface, the wafer needs to be planarized. Planarization isuseful in removing undesired surface topography and surface defects,such as rough surfaces, agglomerated materials, crystal lattice damage,scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing(CMP), is a common technique used to planarize substrates, such assemiconductor wafers. In conventional CMP, a wafer is mounted on acarrier assembly and positioned in contact with a polishing pad in a CMPapparatus. The carrier assembly provides a controllable pressure to thewafer, pressing it against the polishing pad. The pad is moved (e.g.,rotated) relative to the wafer by an external driving force.Simultaneously therewith, a chemical composition (“slurry”) or otherpolishing solution is provided between the wafer and the polishing pad.Thus, the wafer surface is polished and made planar by the chemical andmechanical action of the pad surface and slurry.

Hishiki, U.S. Pat. No. 6,837,781, discloses a polishing pad known in theart manufactured by a RIM process. The polishing pad of Hishiki isformed by dissolving an inert gas in a mixture of polyurethane to createporosity. Unfortunately, polishing pads of Hishiki have large variationsin porosity and may cause unpredictable, and perhaps, detrimental,polishing performances from one polishing pad to the next. For example,Examples 1 and 2 in Table 2 (see cols. 11-12) provided polishing padshaving an average cell diameter of 15 μm and 3 μm, respectively.Further, Examples 3 and 4 in Table 2 provided polishing pads having anaverage cell diameter of 30 μm and 150 μm, respectively. In other words,these polishing pads have variations in porosity of up to about 80percent, which may detrimentally affect polishing performance. Moreover,these variations in porosity may negatively affect polishing performancewithin the pad itself.

Hence, what is needed is a polishing pad made by a reaction-injectionmolding process having improved polishing performance. Moreover, what isneeded is an apparatus and an efficient method of forming a porous, RIMpolishing pad having improved polishing performance.

STATEMENT OF THE INVENTION

In a first aspect of the present invention, there is provided a methodof forming a chemical mechanical polishing pad, comprising: providing atank with polymeric materials; providing a storage silo withmicrospheres; providing a isocyanate storage tank with isocyanates;delivering the polymeric materials and the microspheres to a premix preptank; forming a pre-mixture of the polymeric materials and themicrospheres; delivering the pre-mixture to a premix run tank; forming amixture of the pre-mixture and the isocyanates; injecting the mixtureinto a closed mold; curing the polishing pad in the mold; and degassingat least one of the tank, isocyanate storage tank and the mold.

In a second aspect of the present invention, there is provided a methodof forming a chemical mechanical polishing pad, comprising: providing afirst polyol storage tank with first polymeric materials; providing astorage silo with microspheres; providing a isocyanate storage tank withisocyanates; providing at least a second polyol storage tank with secondpolymeric materials; delivering the first polymeric materials from thefirst polyol storage tank and the microspheres to a premix prep tank;forming a pre-mixture of the first polymeric materials and themicrospheres; delivering the pre-mixture to a premix run tank; forming amixture of the pre-mixture and the isocyanates; providing secondpolymeric materials to the mixture from the at least second polyolstorage tank until a desired bulk density is reached; injecting themixture into a closed mold; curing the polishing pad in the mold; anddegassing at least one of the first and second polyol storage tanks,isocyanate storage tank and the mold.

In a third aspect of the present invention, there is provided a methodof forming a chemical mechanical polishing pad, comprising: providing apolyol storage tank with polymeric materials; providing a storage silowith microspheres; providing a isocyanate storage tank with isocyanates;delivering the polymeric materials and the microspheres to a premixrun/prep tank; forming a pre-mixture of the polymeric materials and themicrospheres; injecting the mixture into a closed mold; curing thepolishing pad in the mold; and degassing at least one of the polyolstorage tank, isocyanate storage tank and the mold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a polishing pad of the present invention;

FIG. 2 illustrates an apparatus for forming the polishing pad of thepresent invention;

FIG. 3 illustrates another embodiment of an apparatus for forming thepolishing pad of the present invention;

FIG. 4 illustrates another embodiment of an apparatus for forming thepolishing pad of the present invention;

FIG. 5 illustrates another embodiment of an apparatus for forming thepolishing pad of the present invention;

FIG. 6 illustrates another embodiment of an apparatus for forming thepolishing pad of the present invention; and

FIG. 7 illustrates a CMP system utilizing the polishing pad of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a reaction-injection molded polishingpad. Further, the present invention provides a novel RIM apparatus andmethod for forming a porous, reaction-injection molded polishing pad. Inparticular, the present invention utilizes a unique premix apparatus toproduce the porous, reaction-injection molded polishing pad. The premixapparatus comprises, a novel premix prep tank for pre-mixing themicrospheres and the polymeric materials (e.g., polyols) to form ahomogeneous pre-mixture. The premix apparatus further comprises a vacuumto remove or degas any mechanically entrained or dissolved gas. Inaddition, the novel reaction-injection molding apparatus providestremendous flexibility in increasing manufacturing scale and in pad-typevariation. In other words, the novel reaction-injection moldingapparatus allows, for example, continuous reaction-injection molding andthe use of almost an endless combination of different polymericmaterials to manufacture the polishing pad of the present invention.

Referring now to FIG. 1, a polishing pad 1 of the present invention isshown. Polishing pad 1 comprises a polishing layer or pad 4, and anoptional bottom layer or pad 2. The bottom layer 2 may be made of feltedpolyurethane, such as SUBA-IV™ pad manufactured by Rohm and HaasElectronic Materials CMP Inc. (“RHEM”), of Newark, DE. The polishing pad4 may comprise a polyurethane pad, such as, OXP 4150™ pad by RHEM.Polishing pad 4 may optionally be texturized as desired. A thin layer ofpressure sensitive adhesive 6 may hold the polishing pad 4 and thebottom layer 2 together. The adhesive 6 may be commercially availablefrom 3M Innovative Properties Company of Saint Paul, Minn. In addition,polishing pad 4 may have a transparent window 14 provided therein tofacilitate end-point detection.

Referring now to FIG. 2, a premix apparatus 100 for forming thepolishing pad 4 of the present invention is shown. The premix apparatus100 comprises a filler storage silo 1 sized to hold a sufficientquantity of microspheres or microelements 48. Premix apparatus 100further comprises a premix prep tank 10 and a storage tank 3 sized tohold a sufficient quantity of polymeric materials 52 (e.g., polyol). Inaddition, premix apparatus 100 advantageously comprises a recirculationloop 16 for controlling the bulk density of the pre-mixture 51 in thepremix prep tank 10. Note, although the premix apparatus 100 isdescribed with reference to a “one tank” system, the invention is not solimited. For example any number of storage silos 1, polyol storages 3and premix prep tanks 10 may be utilized in the present invention, asdesired.

In operation, a predetermined amount of the polymeric materials 52 isadded to the premix prep tank 10. The quantity of the polymericmaterials 52 added to the premix prep tank 10 may be controlled by amass flow metering device 4 with a totalizer (not shown). The quantityof polyol 52 added to the premix prep tank 10 may also be controlled byusing load cells mounted to the premix prep tank 10.

After the polymeric materials 52 are added to the premix prep tank 10,the agitator 18 agitates the polymeric materials 52 to provide anupward, axial flow of the polymeric materials 52 along the shaft of theagitator 18 resulting in a downward flow of the materials 52 along theinner wall of the premix prep tank 10. Alternatively, the polymericmaterials 52 may flow in the opposite direction, as desired. Preferably,the agitator is rotated at a rate of 1 to 500 RPM. More preferably, theagitator is rotated at a rate of 1 to 250 RPM. Most preferably, theagitator is rotated at a rate of 1 to 50 RPM.

Upon activation of the agitator 18, the microspheres 48 in the fillerstorage silo 1 may be added to the premix prep tank 10. In an exemplaryembodiment of the invention, the amount of the microspheres 48 added tothe premix prep tank 10 may be performed by a “loss in weight” dry feedmetering system 2. The dry feed metering system 2 establishes an initialtotal weight of the filler storage silo 1, including the microspheres 48contained within the storage silo 1. Thereafter, a predetermined weightof the microspheres 48 that is to be added to the premix prep tank 10 isset in the dry feed metering system 2. The dry feed metering system 2may then add the microspheres 48 to the premix prep tank 10 until thechange in weight of the filler storage silo 1 matches the desired,predetermined weight of the microspheres 48.

After an appropriate amount of the microspheres 48 is measured out, themicrospheres 48 are added to the polymeric materials 52 and blendedtogether to form a pre-mixture 51, assisted by the agitation of theagitator 18. Advantageously, the ratio of the amount of microspheres 48to that of the polymeric materials 52 is 0 to 50 percent by volume. Moreadvantageously, the ratio of the amount of microspheres 48 to that ofthe polymeric materials 52 is 0 to 40 percent by volume. Mostadvantageously, the ratio of the amount of microspheres 48 to that ofthe polymeric materials 52 is 0.1 to 30 percent by volume.

Advantageously, once the microspheres 48 are blended in the polymericmaterials 52, the pre-mixture 51 is re-circulated in recirculation loop16 to ensure that the pre-mixture 51 remains essentially homogeneous.The recirculation loop 16 helps the pre-mixture 51 to be more uniformlydistributed in the premix prep tank 10 and reduces the potential fordensity stratification. In other words, the recirculation loop 16 allowsfor an efficient method of controlling or stabilizing the bulk densityof the pre-mixture 51.

Advantageously, the recirculation pump 21 draws the pre-mixture 51 fromthe premix prep tank 10 and directs the pre-mixture 51 through adirectional valve 22, the valve 22 returning the pre-mixture 51 back tothe premix prep tank 10. The recirculation pump 21 can be a diaphragm,peristaltic, sine, piston, screw, progressive cavity, lobe or gear typepump requiring no contact lubrication. The bulk density of thepre-mixture 51 can be monitored by manually, periodically sampling thepre-mixture 51 (weight per volume) in conjunction with a scale (notshown).

Optionally, an in-line densitometer 17 may be provided in there-circulation loop 16 to monitor the homogeneity (i.e., density) of thepre-mixture 51. Advantageously, the in-line densitometer 17 provides anautomated method for measuring and displaying the continuous bulkdensity of the pre-mixture 51. The in-line densitometer 17 may measureand display density measurements. The in-line densitometer 17 may becommercially obtained from, for example, Anton Paar of Graz, Austria.The in-line densitometer 17 measures the bulk density (ratio ofmicrospheres 48 to polymeric materials 52) of the pre-mixture 51. If thebulk density is outside a pre-determined, acceptable range, the in-linedensitometer 17 can be used to monitor the addition of eithermicrospheres 48 or polymeric materials 52 to adjust the bulk density ofthe pre-mixture 51 into the desired range.

In operation, the in-line densitometer 17 measures the incoming bulkdensity of the pre-mixture 51 from the directional valve 22. If themeasured bulk density is within acceptable, predetermined tolerances,then the pre-mixture 51 is directed by the directional valve 22 to thetransfer line 20 for further processing. If the measured bulk density istoo high or low, then the pre-mixture 51 is directed by the directionalvalve 22 to the recirculation loop 16, back to the premix prep tank 10,and is not diverted to the transfer line 20. Rather, the pre-mixture 51continues to re-circulate. The density measurement of the pre-mixture 51obtained from the densitometer 17, will be used to provide additionalpolyol 52 or microspheres 48, as desired. Note, the pre-mixture 51 canbe returned to the premix prep tank 10 at any level that does notinterfere with the discharge of the pre-mixture 51 from the bottom ofthe premix prep tank 10. Preferably, the pre-mixture 51 is returned in amanner that reduces the amount of entrained gas being introduced intothe premixture 51, for example, by returning the pre-mixture 51,subsurface to the storage of the pre-mixture 51 in the tank 10 or byreturning the pre-mixture 51 along the inner wall of the tank 10.

Advantageously, the premix prep tank 10 is provided with a vacuum source19 to remove or degas any entrained gas from the addition of themicrospheres 48 to the polymeric materials 52, in order to obtain a moreaccurate bulk density measurement. Preferably, the premix prep tank 10is degassed at a pressure of 1 to 10 torr. More preferably, the premixprep tank 10 is degassed at a pressure of 1 to 5 torr. Most preferably,the premix prep tank 10 is degassed at a pressure of less than 2 torr.In addition, the premix apparatus 100 may further comprise an inert gassource 60 to provide a “blanket” inert gas to the pre-mixture 51 whenthe premix prep tank 10 is not under vacuum from the vacuum source 19.Note, the inert gas is not utilized to create porosity, but rather toreduce them when the vacuum source 19 is turned off.

Preferably, at least a portion of the polymeric microspheres 48 aregenerally flexible. Suitable polymeric microspheres 48 include inorganicsalts, sugars and water-soluble particles. Examples of such polymericmicrospheres 48 (or microelements) include polyvinyl alcohols, pectin,polyvinyl pyrrolidone, hydroxyethylcellulose, methylcellulose,hydropropylmethylcellulose, carboxymethylcellulose,hydroxypropylcellulose, polyacrylic acids, polyacrylamides, polyethyleneglycols, polyhydroxyetheracrylites, starches, maleic acid copolymers,polyethylene oxide, polyurethanes, cyclodextrin, polyacrylonitrile,polyvinylidene chloride, acrylonitrile and vinylidene chloride andcombinations thereof. The microspheres 48 may be chemically modified tochange the solubility, swelling and other properties by branching,blocking, and crosslinking, for example. Preferably, the microspheres 48has a mean diameter that is less than 150 μm, and more preferably a meandiameter of less than 50 μm. Most Preferably, the microspheres 48 has amean diameter that is less than 15 μm. Note, the mean diameter of themicrospheres may be varied and different sizes or mixtures of differentmicrospheres 48 may be impregnated in the polymeric material 52 asdesired. A preferred material for the microsphere is a copolymer ofpolyacrylonitrile and polyvinylidene chloride (e.g., Expancel™ from AkzoNobel of Sundsvall, Sweden).

Additionally, in an exemplary embodiment of the present invention, thepolymeric material 52 of polishing pad 4 is made from ahydroxyl-containing material. Advantageously, the hydroxyl-containingmaterial is a polyol. Exemplary polyols include, but are not limited to,polyether polyols, hydroxy-terminated polybutadiene (includingpartially/fully hydrogenated derivatives), polyester polyols,polycaprolactone polyols, polycarbonate polyols, and mixtures thereof.

In one preferred embodiment, the polyol includes polyether polyol.Examples include, but are not limited to, polytetramethylene etherglycol (“PTMEG”), polyethylene propylene glycol, polyoxypropyleneglycol, and mixtures thereof. The hydrocarbon chain can have saturatedor unsaturated bonds and substituted or unsubstituted aromatic andcyclic groups. Preferably, the polyol of the present invention includesPTMEG. Suitable polyester polyols include, but are not limited to,polyethylene adipate glycol, polybutylene adipate glycol, polyethylenepropylene adipate glycol, o-phthalate-1,6-hexanediol, poly(hexamethyleneadipate) glycol, and mixtures thereof. The hydrocarbon chain can havesaturated or unsaturated bonds, or substituted or unsubstituted aromaticand cyclic groups. Suitable polycaprolactone polyols include, but arenot limited to, 1,6-hexanediol-initiated polycaprolactone, diethyleneglycol initiated polycaprolactone, trimethylol propane initiatedpolycaprolactone, neopentyl glycol initiated polycaprolactone,1,4-butanediol-initiated polycaprolactone, PTMEG-initiatedpolycaprolactone, and mixtures thereof. The hydrocarbon chain can havesaturated or unsaturated bonds, or substituted or unsubstituted aromaticand cyclic groups. Suitable polycarbonates include, but are not limitedto, polyphthalate carbonate and poly(hexamethylene carbonate) glycol.

Additionally, the polymeric material 52 is a polydiamine. Preferredpolydiamines include, but are not limited to, diethyl toluene diamine(“DETDA”), 3,5-dimethylthio-2,4-toluenediamine and isomers thereof,3,5-diethyltoluene-2,4-diamine and isomers thereof, such as3,5-diethyltoluene-2,6-diamine,4,4′-bis-(sec-butylamino)-diphenylmethane,1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline),4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”),polytetramethyleneoxide-di-p-aminobenzoate, N,N′-dialkyldiamino diphenylmethane, p,p′-methylene dianiline (“MDA”), m-phenylenediamine (“MPDA”),methylene-bis 2-chloroaniline (“MBOCA”),4,4′-methylene-bis-(2-chloroaniline) (“MOCA”),4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”),4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”),4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane,2,2′,3,3′-tetrachloro diamino diphenylmethane, trimethylene glycoldi-p-aminobenzoate, and mixtures thereof. Preferably, the polymericmaterial of the present invention includes3,5-dimethylthio-2,4-toluenediamine and isomers thereof. Suitablepolyamines include both primary and secondary amines. Also, blends ofthe above polyols and polydiamines may be utilized.

Optionally, other polymeric materials such as, a diol, triol, tetraol,or hydroxy-terminated isocyanate may be added to the aforementionedpolyurethane composition. Suitable diol, triol, and tetraol groupsinclude ethylene glycol, diethylene glycol, polyethylene glycol,propylene glycol, polypropylene glycol, lower molecular weightpolytetramethylene ether glycol, 1,3-bis(2-hydroxyethoxy) benzene,1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene,1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, resorcinol-di-(beta-hydroxyethyl)ether, hydroquinone-di-(beta-hydroxyethyl) ether, and mixtures thereof.Preferred hydroxy-terminated isocyanates include1,3-bis(2-hydroxyethoxy) benzene,1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene,1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol,and mixtures thereof. Both the hydroxy-terminated and amine isocyanatescan include one or more saturated, unsaturated, aromatic, and cyclicgroups. Additionally, the hydroxy-terminated and amine isocyanates caninclude one or more halogen groups. The polyurethane composition can beformed with a blend or mixture of isocyanates. If desired, however, thepolyurethane composition may be formed with a single isocyanate.

As further discussed below, the polymeric material (e.g.hydroxyl-containing material) is then reacted with a polyisocyanate(e.g., diisocyanate). The polyisocyanate may be aliphatic or aromatic.Preferred polyisocyanates include, but are not limited to, methlene bis4,4′ cyclohexylisocyanate, cyclohexyl diisocyanate, isophoronediisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate,tetramethylene-1,4-diisocyanate, 1,6-hexamethylene-diisocyanate,dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate,cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methylcyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate,triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, uretdione ofhexamethylene diisocyanate, ethylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate(TDI), TDI prepolymer, methylene diphenyl diisocyanate (MDI), crude MDI,polymeric MDI, urethodione-modified MDI, carbodimide-modified MDI, andmixtures thereof. The preferred polyisocyanate is aromatic. Thepreferred aromatic polyisocyanate has less than 14 percent unreactedisocyanate groups.

Optionally, a catalyst may be utilized to decrease the polymerizationreaction time, particularly the gel time and the de-mold time. However,if the reaction is too fast, the material may solidify or gel prior tocomplete filling of the mold. Gel time is preferably in the range of ahalf second to one hour, more preferably in the range of about 1 secondto 5 minutes, more preferably 10 seconds to 5 minutes, and yet morepreferably 30 seconds to 5 minutes. The most preferred catalystscomprise a tertiary amine, such as, diazo-bicyclo-octane. Other usefulcatalysts include, organic acids, organometallics, primary amines andsecondary amines, depending upon the particular reactive chemistrychosen. The catalysts can be di-functional, tri-functional, etc.

Referring now to FIG. 3, a reaction-injection molding apparatus 103,which includes the premix apparatus 100 and a premix run tank 15 as wellas a isocyanate apparatus 101, is illustrated. Isocyanate apparatus 101further comprises a isocyanate run tank 12 and a isocyanate storage tank6. Note, although this embodiment is illustrated with a single premixrun tank 15 and a single isocyanate apparatus 101, any number of premixrun tanks and isocyanate tanks may be utilized, as desired. Inoperation, once a homogeneous blend with an acceptable bulk density isprepared in the premix apparatus 100, the pre-mixture 51 may then betransferred to the premix run tank 15 via the transfer line 20. Thetransfer line 20 can comprise any non-rusting metal, plastic orpolymeric material. This transfer is accomplished by drawing thepre-mixture 51 from the bottom of the premix prep tank 10 using thetransfer pump 21, passing the pre-mixture 51 through the directionalvalve 22, which diverts the flow to the transfer line 20, and sendingthe pre-mixture into the premix run tank 15. Advantageously, once thepre-mixture 51 is transferred from the premix prep tank 10 to the premixrun tank 15, the premix prep tank 10 is available for the preparation ofa new batch of the pre-mixture 51. In addition, the pre-mixture 51contained in the premix run tank 15 is now available forreaction-injection molding. As shown, by having a separate premixpreparation process of the present invention, an uninterruptedreaction-injection molding process is possible.

During reaction-injection molding, the pre-mixture 51 from the premixrun tank 15 and the isocyanate 53 from the isocyanate run tank 12 aremetered to a mixer 13 where the individual components 51, 53 are blendedand molded directly in closed mold 14. The molded article is then curedto form the polishing pad 4 of the present invention. Advantageously,the mold 14 is provided with a vacuum 19 to remove or degas anymechanically entrained gas. The premix run tank 15 and the isocyanaterun tank 12 are also provided with an agitator 18, similar to theagitator 18 of the premix prep tank 10. Additional isocyanate 53 isprovided from a isocyanate storage tank 6 by a level controller 7. Note,any remaining components 51, 53 may be directed back to the respectivetanks 15, 12 by a directional valve 22 for further processing viarecirculation loop 16.

Advantageously, the bulk density of the polishing pad 4 is directlycontrolled by the ratio of the mixture of the two individual components51, 53. The ratio of the mixture of the components 51, 53 from thepremix run tank 15 and the isocyanate run tank 12 is controlled byindividual metering pumps 9 in-conjunction with flow meters 8 containedwithin the delivery line 55.

Accordingly, the present invention provides a method of forming achemical mechanical polishing pad comprising, providing a tank withpolymeric materials, providing a storage silo with microspheres andproviding a isocyanate storage tank with isocyanates. The inventionfurther provides delivering the polymeric materials and the microspheresto a premix prep tank, forming a pre-mixture of the polymeric materialsand the microspheres, delivering the pre-mixture to a premix run tankand forming a mixture of the pre-mixture and the isocyanates. Furtherthe invention provides injecting the mixture into a closed mold, curingthe polishing pad in the mold and degassing at least one of the tank,isocyanate storage tank and the mold.

Referring now to FIG. 4, a reaction-injection molding apparatus 105,which includes a polyol apparatus 104 is illustrated. Polyol apparatus104 further comprises a polyol run tank 11 and a secondary polyolstorage tank 5. In this embodiment, the polyol run tank 11 allows forthe additional, flexible control of the bulk density of the moldedarticle in the reaction-injection molding mold 14. For example, thefinal bulk density ratio of the microspheres 48 to polyol 57 can beadjusted by the addition of a non-filled polyol 57 from the polyol runtank 11 to the mixer 13 along with the component addition from thepremix run tank 15 and the isocyanate run tank 12. The addition of thenon-filled polyol 57 to the mixer 13 is regulated by the flow controlmeter 8 and the metering pump 9. The polyol run tank 11 is also providedwith an agitator 18, similar to the agitator 18 of the premix prep tank10. Additional polymeric materials 57 to the polyol run tank 11 isprovided from a secondary polyol storage tank 5 by the level controller7. Note, although a single polyol run tank 11 is shown, the inventionmay be practiced with any number of additional polyol run tanks, asdesired. In addition, the polyol 57 may be the same as the polyol 52 orany other polymeric material, as desired. Note, any remaining components51, 57, 53 may be directed back to the respective tanks 15, 11, 12 by adirectional valve 22 for further processing via recirculation loop 16.

During reaction-injection molding, the pre-mixture 51 from the premixrun tank 15, the isocyanate 53 from the isocyanate run tank 12 andpolyol 57 from the polyol run tank 11 are metered to a mixer 13 wherethe individual components 51, 53 and 57 are blended and injected into aclosed mold 14. The molded article is then cured to form a polishing pad4 of the present invention. Advantageously, the bulk density of thepolishing pad 4 is directly controlled by the ratio of the mixture ofthe three individual components 51, 53 and 57. The ratio of the mixtureof the components 51, 53 and 57 from the premix run tank 15, theisocyanate run tank 12 and the polyol run tank 11 is controlled byindividual metering pumps 9 in-conjunction with flow meters 8 containedwithin the delivery lines 55.

Advantageously, the polyol run tank 11 and mold 14 are provided with avacuum 19 to remove or degas any mechanically entrained gas.Additionally, the premix run tank 15 and the isocyanate run tank 12 arealso provided with a vacuum 19. Preferably, the premix prep tank 10 isdegassed at a pressure of 1 to 10 Torr. More preferably, the premix preptank 10 is degassed at a pressure of 1 to 5 Torr. Most preferably, thepremix prep tank 10 is degassed at a pressure of less than 2 Torr.

Accordingly, the present invention provides a method of forming achemical mechanical polishing pad, comprising the steps of, providing afirst polyol storage tank with first polymeric materials, providing astorage silo with microspheres, providing a isocyanate storage tank withisocyanates and providing at least a second polyol run tank with secondpolymeric materials. Further, the method provides the steps of,delivering the polymeric materials from the first polyol storage tankand the microspheres to a premix prep tank, forming a pre-mixture of thefirst polymeric materials and the microspheres, and delivering thepre-mixture to a premix run tank. The method further provides the stepsof forming a mixture of the pre-mixture and the isocyanates, providingsecond polymeric materials to the mixture from the at least secondpolyol run tank until a desired bulk density is reached, injecting themixture into a closed mold and curing the polishing pad in the mold.Finally, the invention further provides degassing at least one of thefirst and second polyol storage tanks, isocyanate storage tank and themold.

Referring now to FIG. 5, a reaction-injection molding apparatus 107comprising a premix run/prep apparatus 106 and a isocyanate apparatus101, is illustrated. Premix run/prep apparatus 106 further comprises afiller storage silo 1 sized to hold a sufficient quantity ofmicrospheres or microelements 48. Premix run/prep apparatus 106 furthercomprises a premix run/prep tank 59 and a polyol storage tank 3 sized tohold a sufficient quantity of polymeric material 52. In addition, premixrun/prep apparatus 106 advantageously comprises a recirculation loop 16for controlling the bulk density of the premixture 51 in the premixrun/prep tank 59. Note, in contrast to the embodiments of FIGS. 2, 3 and4, the embodiment of FIG. 5 (and FIG. 6, below) provides a premix preptank and a premix run tank in a single run/prep tank. In other words,the embodiment of FIG. 5 (and FIG. 6) eliminates the need for a“transfer step” between the premix prep tank and the premix run tank.Note, however, that while this embodiment allows for batchreaction-injection molding of the polishing pad of the presentinvention, it does not allow for continuous reaction-injection molding.

In operation, a predetermined amount of the polymeric materials 52 isadded to the premix run/prep tank 59. The quantity of the polymericmaterials 52 added to the premix run/prep tank 59 may be controlled by amass flow metering device 4. The quantity of polyol 52 added to thepremix run/prep tank 59 may also be controlled by using load cellsmounted to the premix run/prep tank 59.

After the polymeric materials 52 are added to the premix run/prep tank59, the agitator 18 agitates the polymeric materials 52 to provide anupward, axial flow of the polymeric materials 52 along the shaft of theagitator 18 resulting in a downward flow of the polymeric materials 52along the inner wall of the premix run/prep tank 59. Preferably, theagitator is rotated at a rate of 1 to 500 RPM. More preferably, theagitator is rotated at a rate of 1 to 250 RPM. Most preferably, theagitator is rotated at a rate of 1 to 50 RPM.

Upon activation of the agitator 18, the microspheres 48 in the filestorage silo 1 may be added to the premix run/prep tank 59. In anexemplary embodiment of the invention, the amount of the microspheres 48added to the premix run/prep tank 59 may be performed by a “loss inweight” dry feed metering system 2. The dry feed metering system 2establishes an initial total weight of the filler storage silo 1,including the microspheres 48 contained within the storage silo 1.Thereafter, a predetermined weight of the microspheres 48 that is to beadded to the premix prep tank 10 is set in the dry feed metering system2. The dry feed metering system 2 may then add the microspheres 48 tothe premix prep tank 10 until the change in weight of the filler storagesilo 1 matches the desired, predetermined weight of the microspheres 48.

After an appropriate amount of the microspheres 48 is measured out, themicrospheres 48 are added to the polymeric materials 52 and blendedtogether to form a pre-mixture 51, assisted by the agitation of theagitator 18. Advantageously, the ratio of the amount of microspheres 48to that of the polymeric materials 52 is 0 to 50 percent by volume. Moreadvantageously, the ratio of the amount of microspheres 48 to that ofthe polymeric materials 52 is 0 to 40 percent by volume. Mostadvantageously, the ratio of the amount of microspheres 48 to that ofthe polymeric materials 52 is 0.1 to 30 percent by volume.

Advantageously, once the microspheres 48 are blended in the polymericmaterials 52, the pre-mixture 51 is re-circulated in recirculation loop16 to ensure that the pre-mixture 51 remains essentially homogeneous.The recirculation loop 16 helps the pre-mixture 51 to be more uniformlydistributed in the premix run/prep tank 59 and reduces the potential fordensity stratification. In other words, the recirculation loop 16 allowsfor an efficient method of controlling the bulk density of thepre-mixture 51. The bulk density of the pre-mixture 51 can be monitoredby manually, periodically sampling the pre-mixture 51 in conjunctionwith a scale (not shown).

Advantageously, the recirculation pump 21 draws the pre-mixture 51 fromthe premix run/prep tank 59 and directs the pre-mixture 51 through adirectional valve 22, the valve 22 returning the pre-mixture 51 back tothe premix run/prep tank 59. The recirculation pump 21 can be adiaphragm, peristaltic, sine, or lobe type pump requiring no contactlubrication. Optionally, an in-line densitometer 17 may be provided inthe re-circulation loop 16 to monitor the homogeneity of the pre-mixture51. Advantageously, the in-line densitometer 17 provides an automatedmethod for measuring the continuous bulk density of the pre-mixture 51.The in-line densitometer 17 may measure and display densitymeasurements. The in-line densitometer 17 measures the bulk density(ratio of microspheres 48 to polymeric materials 52) of the pre-mixture51. If the bulk density is outside a pre-determined, acceptable range,the in-line densitometer 17 can be used to monitor the addition ofeither microspheres 48 or polymeric materials 52 to adjust the bulkdensity of the pre-mixture 51 into the desired range.

In operation, the in-line densitometer 17 measures the incoming bulkdensity of the pre-mixture 51 from the directional valve 22. If thecalculated bulk density is within acceptable, predetermined tolerances,then the measured pre-mixture 51 is directed by the directional valve 22to the delivery line 55. If the calculated bulk density is too high orlow, then the measured pre-mixture 51 is directed by the directionalvalve 22 to the recirculation loop 16, back to the premix run/prep tank59, to be agitated again. In other words, if the bulk density is toohigh, then additional agitation is conducted. Note, the pre-mixture 51can be returned to the premix run/prep tank 59 at any level that doesnot interfere with the discharge of the pre-mixture 51 from the bottomof the premix run/prep tank 59.

Advantageously, the premix run/prep tank 59 is provided with a vacuum 19to remove or degas any entrained gas from the addition of themicrospheres 48 to the polymeric materials 52, in order to obtain a moreaccurate bulk density measurement. Preferably, the premix run/prep tank59 is degassed at a pressure of 1 to 10 Torr. More preferably, thepremix prep tank 10 is degassed at a pressure of 1 to 5 Torr. Mostpreferably, the premix prep tank 10 is degassed at a pressure of lessthan 2 Torr.

Referring still to FIG. 5, the isocyanate apparatus 101 furthercomprises a isocyanate run tank 12 and a isocyanate storage tank 6.Note, although this embodiment is illustrated with a single isocyanateapparatus 101, any number of isocyanate apparatuses may be utilized, asdesired. During reaction-injection molding, the pre-mixture 51 from thepremix run/prep tank 59 and the isocyanate 53 from the isocyanate runtank 12 are metered to a mixer 13 where the individual components 51, 53are blended and molded directly into a closed mold 14. The moldedarticle is then cured to form the polishing pad 4 of the presentinvention. Advantageously, the mold 14 is provided with a vacuum 19 toremove or degas any mechanically entrained gas. Note, any remainingcomponents 51, 53 may be directed back to the respective tanks 59,12 bya directional valve 22 for further processing via recirculation loop 16.The premix run/prep tank 59 and the isocyanate run tank 12 are alsoprovided with an agitator 18, similar to the agitator 18 of the premixprep tank 10. Additional isocyanate 53 is provided from a isocyanatestorage tank 6 by a level controller 7. Advantageously, the bulk densityof the polishing pad 4 is directly controlled by the ratio of themixture of the two individual components 51, 53. The ratio of themixture of the components 51, 53 from the premix run/prep tank 59 andthe isocyanate run tank 12 is controlled by recirculation pump 21 andmetering pump in-conjunction with flow meters 8 contained within thedelivery line 55.

Referring now to FIG. 6, a reaction-injection molding apparatus 109comprising a secondary polyol apparatus 111, is illustrated. Polyolapparatus 111 further comprises a secondary polyol run tank 11 and asecondary polyol storage tank 5. In this embodiment, the polyol run tank11 allows for the additional, flexible control of the molded article inthe reaction-injection molding mold 14. For example, the final bulkdensity ratio of the microspheres 48 to polyol 52 can be adjusted by theaddition of a non-filled polyol 57 from the polyol run tank 11 to themixer 13 along with the component addition from the premix run/prep tank59 and the isocyanate run tank 12. The addition of the non-filled polyol57 to the mixer 13 is regulated by the flow control meter 8 and themetering pump 9. The polyol run tank 11 is also provided with anagitator 18, similar to the agitator 18 of the premix prep tank 10.Additional polymeric materials 57 to the polyol run tank 11 is providedfrom the secondary polyol storage tank 5 by the level controller 7.Note, although a single polyol run tank 11 is shown, the invention maybe practiced with any number of additional polyol run tanks, as desired.In addition, the polyol 57 may be the same as the polyol 52 or any otherpolymeric material, as desired.

During reaction-injection molding, the pre-mixture 51 from the premixrun/prep tank 59, the isocyanate 53 from the isocyanate run tank 12 andnon-filled polyol 57 from the polyol run tank 11 are metered to a mixer13 where the individual components 51, 53 and 57 are blended and moldeddirectly into a mold 14. The molded article is then cured to formpolishing pad 4 of the present invention. Advantageously, the bulkdensity of the polishing pad 4 is directly controlled by the ratio ofthe mixture of the three individual components 51, 53 and 57. The ratioof the mixture of the components 51, 53 and 57 from the premix run/preptank 59, the isocyanate run tank 12 and the polyol run tank 11 iscontrolled by individual metering pumps 9 in-conjunction with flowmeters 8 contained within the delivery line 55.

Advantageously, the polyol run tank 11 and mold 14 are provided with avacuum 19 to remove or degas any mechanically entrained gas.Additionally, the premix run/prep tank 59 and the isocyanate run tank 12are also provided with a vacuum 19. Preferably, the premix prep tank 10is degassed at a pressure of 1 to 10 Torr. More preferably, the premixprep tank 10 is degassed at a pressure of 1 to 5 Torr. Most preferably,the premix prep tank 10 is degassed at a pressure of less than 2 Torr.

Accordingly, the present invention provides a method of forming achemical mechanical polishing pad, comprising the steps of providing apolyol storage tank with polymeric materials, providing a storage silowith microspheres and providing a isocyanate storage tank withisocyanates. The method further provides the steps of, delivering thepolymeric materials and the microspheres to a premix run/prep tank,forming a pre-mixture of the polymeric materials and the microspheres.The method further provides the steps of, forming a mixture of thepre-mixture and the isocyanates, injecting the mixture into a closedmold and curing the polishing pad in the mold. Finally, the presentinvention provides degassing the polyol storage tank, isocyanate storagetank and the mold.

Referring now to FIG. 7, a CMP apparatus 73 utilizing thereaction-injection molded polishing pad of the present invention isprovided. Apparatus 73 includes a wafer carrier 81 for holding orpressing the semiconductor wafer 83 against the polishing platen 91. Thepolishing platen 91 is provided with a stacked polishing pad 1,including the reaction-injection molded polishing pad 4 of the presentinvention. As discussed above, pad 1 has a bottom layer 2 thatinterfaces with the surface of the platen 91, and a polishing pad 4 thatis used in conjunction with a chemical polishing slurry to polish thewafer 83. Note, although not pictured, any means for providing apolishing fluid or slurry can be utilized with the present apparatus.The platen 91 is usually rotated about its central axis 79. In addition,the wafer carrier 81 is usually rotated about its central axis 75, andtranslated across the surface of the platen 91 via a translation arm 77.Note, although a single wafer carrier is shown in FIG. 7, CMPapparatuses may have more than one spaced circumferentially around thepolishing platen. In addition, a transparent hole 87 is provided in theplaten 91 and overlies the window 14 of pad 1. Accordingly, transparenthole 87 provides access to the surface of the wafer 83, via window 14,during polishing of the wafer 83 for accurate end-point detection.Namely, a laser spectrophotometer 89 is provided below the platen 91that projects a laser beam 85 to pass and return through the transparenthole 87 and window 14 for accurate end-point detection during polishingof the wafer 83.

Accordingly, the present invention provides a method of forming achemical mechanical polishing pad comprising the steps of, providing atank with polymeric materials, a storage silo with microspheres and aisocyanate storage tank with isocyanates. Further, the method includesdelivering the polymeric materials and the microspheres to a premix preptank and forming a pre-mixture of the polymeric materials and themicrospheres. The method further provides the steps of delivering thepre-mixture to a premix run tank, forming a mixture of the pre-mixtureand the isocyanates, injecting the mixture into a closed mold and curingthe polishing pad in the mold. Finally, the invention further providesdegassing at least one of the polyol storage tank, isocyanate storagetank and the mold.

1. A method of forming a chemical mechanical polishing pad, comprising:providing a tank with polymeric materials; providing a storage silo withmicrospheres; providing an isocyanate storage tank with isocyanates;delivering the polymeric materials and the microspheres to a premix preptank; forming a pre-mixture of the polymeric materials and themicrospheres; delivering the pre-mixture to a premix run tank; forming amixture of the pre-mixture and the isocyanates; injecting the mixtureinto a closed mold; curing the polishing pad in the mold; and degassingat least one of the tank, isocyanate storage tank and the mold.
 2. Themethod of claim 1 further comprising recirculating the pre-mixture untila desired bulk density is reached.
 3. The method of claim 1 furthercomprising agitating the pre-mixture in the premix prep tank with anagitator.
 4. The method of claim 1 wherein the microsphere comprisespolyvinyl alcohols, pectin, polyvinyl pyrrolidone,hydroxyethylcellulose, methylcellulose, hydropropylmethylcellulose,carboxymethylcellulose, hydroxypropylcellulose, polyacrylic acids,polyacrylamides, polyethylene glycols, polyhydroxyetheracrylites,starches, maleic acid copolymers, polyethylene oxide, polyurethanes,cyclodextrin, polyacrylonitrile, polyvinylidene chloride, copolymers ofacrylonitrile and vinylidene chloride and combinations thereof.
 5. Themethod of claim 1 wherein the polymeric material comprises,polytetramethylene ether glycol, polyethylene propylene glycol,polyoxypropylene glycol, polyethylene adipate glycol, polybutyleneadipate glycol, polyethylene propylene adipate glycol,o-phthalate-1,6-hexanediol, poly(hexamethylene adipate) glycol,1,6-hexanediol-initiated polycaprolactone, diethylene glycol initiatedpolycaprolactone, trimethylol propane initiated polycaprolactone,neopentyl glycol initiated polycaprolactone, 1,4-butanediol-initiatedpolycaprolactone, PTMEG-initiated polycaprolactone, polyphthalatecarbonate, poly(hexamethylene carbonate) glycol, diethyl toluene diamine(“DETDA”), 3,5-dimethylthio-2,4-toluenediamine and isomers thereof,3,5-diethyltoluene-2,4-diamine and isomers thereof, such as3,5-diethyltoluene-2,6-diamine,4,4′-bis-(sec-butylamino)-diphenylmethane,1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline),4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”),polytetramethyleneoxide-di-p-aminobenzoate, N,N′-dialkyldiamino diphenylmethane, p,p′-methylene dianiline (“MDA”), m-phenylenediamine (“MPDA”),methylene-bis 2-chloroaniline (“MBOCA”),4,4′-methylene-bis-(2-chloroaniline) (“MOCA”),4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”),4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”),4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane,2,2′,3,3′-tetrachloro diamino diphenylmethane, trimethylene glycoldi-p-aminobenzoate, and blends thereof.
 6. The method of claim 1 whereinthe isocyanate comprises, methylene bis 4,4′ cyclohexylisocyanate,cyclohexyl diisocyanate, isophorone diisocyanate, hexamethylenediisocyanate, propylene-1,2-diisocyanate,tetramethylene-1,4-diisocyanate, 1,6-hexamethylene-diisocyanate,dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate,cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methylcyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate,triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, uretdione ofhexamethylene diisocyanate, ethylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate(TDI), TDI prepolymer, methylene diphenyl diisocyanate (MDI), crude MDI,polymeric MDI, urethodione-modified MDI, carbodimide-modified MDI, andmixtures thereof.
 7. The method of claim 1 wherein the tank furthercomprises a catalyst.
 8. A method of forming a chemical mechanicalpolishing pad, comprising: providing a first polyol storage tank withfirst polymeric materials; providing a storage silo with microspheres;providing an isocyanate storage tank with isocyanates; providing atleast a second polyol storage tank with second polymeric materials;delivering the first polymeric materials from the first polyol storagetank and the microspheres to a premix prep tank; forming a pre-mixtureof the first polymeric materials and the microspheres; delivering thepre-mixture to a premix run tank; forming a mixture of the pre-mixtureand the isocyanates; providing second polymeric materials to the mixturefrom the at least second polyol storage tank until a desired bulkdensity is reached; injecting the mixture into a closed mold; curing thepolishing pad in the mold; and degassing at least one of the first andsecond polyol storage tanks, isocyanate storage tank and the mold. 9.The method of claim 8 wherein the first and second polymeric materialsare the same.
 10. A method of forming a chemical mechanical polishingpad, comprising: providing a polyol storage tank with polymericmaterials; providing a storage silo with microspheres; providing anisocyanate storage tank with isocyanates; delivering the polymericmaterials and the microspheres to a premix run/prep tank; forming apre-mixture of the polymeric materials and the microspheres; injectingthe mixture into a closed mold; curing the polishing pad in the mold;and degassing at least one of the polyol storage tank, isocyanatestorage tank and the mold.